Since glucocorticoid exerts its biological effects by binding to its receptor, the expression efficiency of the glucocorticoid receptor (GR) gene could influence glucocorticoid sensitivity. We found a polymorphism of cytosine/adenine (-22 C/A) in the upstream region of the GR gene. There was no difference in the allelic frequency between normal and type 2 diabetic subjects. The promoter activity determined by luciferase assay was significantly lower in the -22 A allele than in the -22 C allele in both HepG2 (A allele, 4.19 +/- 0.15; C allele, 6.07 +/- 0.27, p < 0.001) and human embryonic kidney 293 cell lines (A allele, 0.93 +/- 0.16; C allele, 1.51 +/- 0.32, p < 0.001). This polymorphism is associated with transcription of the CR gene, which could be related to glucocorticoid sensitivity through an alteration in tissue GR number.